Radio control system



L. B. BRlTTAlN RADIO CONTROL SYSTEM Filed Feb. 25, 1942 INVENTOR Loa/ 5. //f/'n BY MTTORNEY Aug. 17, 1948.

Patented Aug. 17, 1948 UNITED :STATES TENT OFFICE nacio coN'rnoL SYSTEM Louis B. Brittain, Los Angeles, Calif. Application February 23, 1942, Serial No. 431,909

are now very extensively used, and are uniformly By appropriate direction finding apparatus,

those broadcasting stations, if on the air, can serve quite effectively to guide enemy war planes to their objectives. Accordingly in time of war, broadcasting stations in a certain locality are ordered on the air just as soon as unidentied or enemy planes are detected in that locality, indicating an imminent air raid. The cessation of broadcasting therefore is, to the public, a forewarning of an air raid.

This iorewarning is of particular importance to place the members of civilian defense on the alert; but when the broadcasting stations go ofi the air, often those most concerned with this do not have their radio sets in operation.

It is one of the objects of this invention to make it possible to operate a signal or a control device, such as a relay,'upon c'essationof 'broadcasting; and particularly to accomplish this result While the radio set is silent. f Y

It is another object of this invention to make it possible to use a standard set, with the addition merely of a few inexpensive parts, to eiiect the desired results.

In order to accomplish these objects, the in-J vention contemplates the use of the carrier wave energy received from a specic tuned-in station,V

to render the set ineffective; andas soon as the carrier wave ceases, the set can operate to pro-` duce a signal or control eiectLsuch as for eX` ample through the usual loud speaker or by-aid of arrelay device. 1 a

More speciiically, almost all radio receivers are now provided with automaticfvolume lcontrol circuits. These are usually so 4arranged that when the signal strength reaches a high limit, the'V the negative bias is nolonger created, and energy can flow to the output, as by the aid voi a regenerative or feed-back circuit, causing the`v loud- 8 Claims. (Cl. Z50-20) speaker to produce a tone of a pitch determined by the intensity of the current. Placing the set in a condition to respond to cessation of .broadcasting, while yet remaining silent, is simply effected by the aid of a switch.' This switch can be placed in a vposition where the set operates to reproduce the broadcast, or in another position, reducing the iiow'of energy to the loud speaker, while the set is turned on, and yet conditioning the circuits so that fan audible signal is received as soon as broadcasting ceases. Y

in another form of the invention, the carrier vave operating serves to' cause a flow of energy throughn an amplier system suiiicient to operate a relay. Such la rel-ay may be used to Adeenergize sources of light automatically, asV for black-out purposes. f

This invention possesses many other advantages, and Yhas other objects which may be made more readily apparent from a consideration of several embodiments of theY` invention. YFor this purpose there are shown a few iorms in the drawings accompanying and forming part ofthe present specification. These forms will now be described in detail, illustrating the general principles of the invention; but it is to beY understood that'this detailed description is not to be taken in -a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a wiring diagram illustrating one form of the invention; and

Fig. 2' is a fragmentary wiring diagram of a modified form of the invention.

' In the present instance, the invention is illustrated Yin connection with a conventional type of superheterodyne radio receiver. However, the invention may be incorporated in connection with other types of receivers.

`The wiring diagram of Fig. 1 shows in general various units of such a conventional superheterodyne receiving` system. Thus for example there is illustrated a pickup I which may be in the form of an vantenna circuit or a loop circuit. This pick-y up l is shown as connected to a tunable radio frequency amplifier system 2. The output of this radio-frequency.ampliersystem is connected to a converter 3 which usually comprises an oscillator and a rst detector. The output of the converter is connected to the intermediate frequency ampliiier system 4.

Since the particular scheme of connections is unimportant, these various elements l, 2V, 3 Iand 4 are shown in the form o1 block diagrams.

The output of the intermediate frequency amplifier system is shown as connected to a system 5 that comprises the sound detector as well as a source or" automatic volume control voltage. This system 5 is arranged in any well known manner to develop a voltage, usually of negative character, which may be impressed upon the control electrodes of at least some of the amplifier tubes in the preceding stages 2, 3 and 4, for the purpose of limiting the degree of amplication. Since these systems 2, 3, 4- and 5 are provided with ground connections as illustrated, the automatic volume control voltage can be made ellec-` tive by the aid of a conductor 6 leading from the system 5, and branching olif to appropriate amplifier tubes in the systems 2, 3 and 4. This automatic Volume control voltage is impressed upon the control electrodes of some of the tubes included in the stages 2, 3 and B.

While a conventional form of automatic Volume control system is indicated, for the purposes of the present invention, a control voltage may be created in any other known manner, by the operation of the carrier wave received by the pickup System I,

When the entire system is operating as a conventional radio receiving system, the output of the system 5 may be connected to the input circuit of an audio frequency amplifier l. This is shown as a conventional triode, although other types of tubes .might be utilized. The input circuit of the amplifier tube 'I is connected to the system 5 through a switch 8 located between the control electrode or grid 9 and one of the output leads of the system 5. The cathode Il) of the ampliiier 'I is shown as connected to the other output lead of the system 5. The audio frequency amplifier 'I is shown as coupled in any desired manner to the input circuit of a power tube II, also sho-wn for the sake of simplicity as a triode. The output circuit of the tube II includes the primary winding I2 of an iron core transformer I3. The secondary winding I4 is shown 'as connected to operate a sound reproducer such as the loud speaker I5.

The anodes of tubes I and II are arranged to be connected to a conventional source of direct current potential, in a well understood manner. Furthermore, the cathodes of both tubes 'I and I I, as well as one of the terminals of the secondary winding I4, are all connected to ground as indicated at I6.

In the normal use of the receiving set, the switch 8 is thrown to the full line position and the set operates in a well understood manner. If, however, the switch 8 is thrown to the dotted line position, reception of a carrier wave maintains the set silent. Upon cessation of the carrier waves, the loud speaker I5 is caused to emit a sound signal. The manner in which this is accomplished will now be described.

Since switch 8, when in the dotted line position, disconnects the input circuit or audio fren quency amplifier 'I from the output of the system 5, the set is no longer operative as a conventional receiver set. By placing the switch 8 in the dotted line position so as to connect the control electrode 9 to the conductor I'I, this control electrode 9 is biased with the automatic volume control voltage. This biasing is in such a direction, usually negative, as to cause a greatly reduced output voltage across the output circuit of the ampliiier 1. Thus the automatic volume control lead 3 is shown as connected by the aid of the conductor I8 and resistance I9 to the connection Il and by way of switch 8 to the electrode 9. Accordingly while the carrier wave is being received the transmission off signaling impulses is substantially entirely blocked through the ampliiier When the carrier wave ceases, however, this blocking potential is no longer created. The amplier 'I -is then rendered sufliciently active to cause oscillations in a regenerative or feed-back circuit. This regenerative circuit includes a coupling between the input of tube 'I and the output of tube II. This is accomplished by the aid of the connection 2Il in which is included a capacitance ZI las Well as a variable resistance 22. The regenerative or feed-back coupling thus includes the control electrode 9, the resistance 22, capacitance 2i and the inductance I il. Accordingly when this switch 8 is in the dotted line position and the carrier wave goes off the air, the loud speaker i5 is rendered active by the oscillations of current produced through the Ycooperation of the regenerative circuit with the tubes 'l and I I.

The pitch and amplitude of the sound produced by the loud speaker I5 when the regenerative circuit is active depends upon the capacity of the capacitance 2l as well as the value of the resistance 2.2. This may be :purposely made adjustable for controlling the eedeback circuit.

The resistance I9 is also indicated as variable. This resistance has no eiect upon the biasing voltage appliedA to the control electrode 8; but together with the resistance 22 it determines the amount of feed-back between the output and input'oircuits of the system comprising the tubes 'l' and I I. In ordinary instances the resistance I 3 may be of the order of ten thousand or less ohms and'may be asV high as one hundred thousand ohms. Similarly the resistance 22 may be of the order of thirty thousand ohms to three million ohms. The capacity of the capacitance 2l may be of the order .001 microfaradto as high as .01 microfarad. `0f course these values are dependent to some extent upon the other constants of the system.

It is not essential to utilize a feed-back or regenerative circuit to obtain a signaling or controlling unction. Thus in the form of the invention illustrated in Fig. 2, an electromagnetically operated relay mechanism '23 is illustrated. This relay may include front and back contacts 2li and 29. The relay mechanism 23 includes an electromagnet 25 located in the output circuit of a power tube 26. This power tube has its input circuit connected to the output circuit of the amplier 2 1. The plate current in tube 27 provides a grid bias for tube 216, as by the aid oi the resistances 30, 3I, 32.

The ampliiier 21 is shown as having a control electrode 28 corresponding to the control electrode 9 of the first form of the invention. The switch 8 in the 'full line position serves to impress upon the input side of the amplifier 2l the signaling impulses received by the radio receiving set. In the dotted line position the switch 8 connectsthe electrode 28 to a source of biasing voltage such as the'automatic volume control voltage. When the carrier wave is active the plate current in tube 21 is a minimum ldue to the grid bias on the grid-28. Accordingly, the grid bias on power tube 26 is also a minimum and consequently the Current in tube 26 is a maximum and the relay 23 is held in the position indicated, the electromagnet 25 being energized. Should the carrier wave disappear, the current increase in the plate circuit of tube 2'I causes an increase of bias on the grid of tube 26 and the resultant decrease in the plate current in tube 26 permits the relay to open.

In this way, a failure in the receiver or its power supply automatically causes the relay '23 to operate, which provides a safety factor.

What is claimed is: y

1. In a radio receiving system utilizing a series of electronic emission tubes cooperating with a translating device, each of said tubes having an input side, means responsive to the reception of a carrier Wave by said system for creating a potential difference, means for disconnecting the input side of one of the tubes so that the system is rendered incapable of transmitting signaling impulses, and for connecting said input side to the means creating a potential difference, said potential diierence, when it exists, being of such direction and value as to block the transmission of energy through said tube, and means cooperating With said tube for causing energization of said translating device upon cessationof said blocking eiect.

2. In combination with a radioreceiver of the type having a plurality of electronic emission tubes adapted to cooperate with a translating device, each of said tubes having a control electrode, and an automatic volume control by the aid of which a potential difference is created in response to the reception of a carrier wave by said receiver, said potential difference being applied as a control electrode bias to at least one of said tubes ahead of the last tube: means adapted to form a regenerative circuit, including said last tube as Well as a circuit controller for optionally connecting the control electrode of said tube with said means, or in signal receiving relation with the other tube or tubes, and means for applying at least a part of said potential difference to the regenerative circuit so as to be effective on the control electrode of said last tube, said potential difference, when it exists, being oi such direction and magnitude as to cause a reduction in the supply of signalling voltage to the transl-ating device to render said device substantially inactive, the constants of said regenerative circuit being such that, upon cessation of the carrier Wave, the regenerative circuit operatively affects the translating device.

3. In combination with a radio receiver of the type having at least a pair of electronic emission tubes adapted to cooperate with a sound reproducer, each of said tubes having a control electrode: means responsive to the reception of a carrier wave by said receiver for creating a potential diiierence, and circuit forming means adapted to be connected to the control electrode of one of said tubes, and when so connected serving to apply said potential difference to said electrode, as Well as to form a regenerative circuit including said tube, said potential difference, when it exists, being of such direction and magnitude as to cause a reduction in the supply of signalling current to the sound reproducer, said regenerative circuitJ having constants such that said circuit is effective to energize said sound reproducer only when said potential diierence is substantially non-existent.

4. In combination with a radio .receiver of the type having at least a pair of electronic emission tubes adapted to cooperate with a sound reproducer, each of said tubes having a control electrode: means responsive to the reception of a carrier Wave by said receiver for creating a potential difference, circuit forming means adapted to be connected to the control electrode of one of said tubes, and'When so connected serving to apply said potential difference to said electrode, as

6. well as to form a regenerative circuit including said tube, said potential diiference, when it eX- ists, being of such direction and magnitude as to cause a reduction in the supply of signalling current to the sound reproducer, Vsaid regenerative circuit having constants such that said circuit is eiective to energize said sound reproducer only when said potential difference is substantially non-existent, and a common circuit controller for optionally connecting said electrode with said circuitl forming means, as Well as for causingsaid potential difference to become effective on said electrode, or to receive signalling current from a preceding tube. v

5. In combination with a radio receiver of the type having a series of electronic emission tubes adapted to cooperate with a sound reproducer, each of said tubes having a control electrode and an anode, said receiver also having an automatic volume control responsive to the existence of a carrier Wave to apply a potential difference on at least one of said tubes ahead of the last tube of the series, for limiting the volume: a pair of circuit forming means optionally rendered eiective, one circuit of said pair serving to transmit signalling impulses in a normal manner to said last tube, the other circuit serving to impress at least part of said potential difference on one of said tubes beyond the said prior tube or tubes, said potential difference, when it exists, being of such direction and magnitude as to render said one tube ineiectiveto cause operation of the sound reproducer, said other circuit including a connection between the control electrode and the anode of said tube for causing said tube to oscillate and cause operation of the sound reproducer when said potential diierence is nonexistent due tothe cessation of the Vcarrier Wave.

6. In combination with a radio receiver of the type having a series of electronic emission tubes adapted to cooperate with a sound reproducer, each of said tubes having a control electrode and an anode, said receiver also having an automatic volume control responsive to the existence of a carrier Wave to apply a potential difference on at least one of said tubes ahead of the last tube of the series, for limiting the volume: a circuit forming means including a circuit controller and adapted to connect said volume control means to the control electrode of one tube of said series beyond those having automatic volume control, said connection serving to impress a biasing potential sufficient, While the carrier Wave exists, to render said one tube ineffective to cause operation of said sound reproducer, and means forming a regenerative circuit including said one tube, and causing, during cessation of said carrier wave, oscillations that operate the sound reproducer.

7. In signalling apparatus utilizing a series of electronic emission tubes adapted to cooperate with a translating device, at least one of said tubes having a control electrode, said tube being unable to transmit ampliiied signalling impulses of a carrier Wave received by said apparatus to said translating device, means operative to create a'potential difference in response to the reception of said carrier Wave, and means optionally connecting said control electrode to a signal translating circuit or to said potential difference creating means for impressing said potential difference upon said control electrode, said potential difference, when it exists, being of such direction and magnitude as to block transmission of energy through said tube to the translating device,

and ineffective 4to block such transmission when the carrier Wave ceases.

8. In signalling apparatus utilizing a series of electronic emission tubes adapted to cooperate with a translating device, at least one of said tubes having a control electroda'said tube being unable to transmit amplified signalling impulses of a carrier Wave received by said "apparatus to said translating device, means operative to create a potential Adiierence in response to the reception of s id carrier Wave, means optionally connecting .aid control electrode to a signal translating circ .it or to said potential diierence creating mea-.s for impressing said potential difference upon said control electrode, said potential diiTerence, when it exists, being of such direction and magnitude as to block transmission of energy through said tube to the translating device, and ineffective to block euch transmission when the REFERENCES CITED The following references are of record in the file of this patent:

UNTED STATES PATENTS Number Name Date 1,489,158 Schaffer Apr. 1, 1924 1,522,581 Espenschied Jan. 13, 1925 2,125,468 Sinninger Aug. 2,1938 2,156,809 Fredrickson May 2, 1939 2,200,037 Mountjoy et al May 7, 1940 2,204,962 Hildebrandt June 13, 1940 2,367,378 Schick Jan. 16, 1945 

